Optical disks may generally be used as removable media for retrieving and storing digital information, e.g. data, audio and video. Optical disks may be classified into disk types according to disk generations into Compact Disc (CD), Digital Versatile Disc (DVD) and Blu-Ray Disc (BD). Optical disks may further or alternatively be classified into read-only (ROM) disks and writable disks. Writable disks may further be classified into recordable (R) and rewritable (RW, RE, RAM) disks. Currently trends include miniaturizing a spot diameter using a high numerical aperture (NA) objective lens and using increasingly shorter wavelength light sources.
An optical disk drive may be arranged to handle optical disks of multiple generations and multiple disk types. An optical disk drive may e.g. be arranged to read and write CD-generation disks, DVD-generation disks as well as BD-generation disks. An optical disk drive may further be arranged to read read-only disks of one or more disk generations, e.g. CD-ROM, DVD-ROM and BD-ROM disks. An optical disk drive may further be arranged to e.g. read and write a plurality of writable disks of one or more disk generations. An optical disk drive may further be arranged to e.g. read and/or write at least a plurality of DVD-types, e.g. DVD-R, DVD-RW, DVD+R, DVD+RW and DVD-Qflix disks, optionally in a plurality of speed grades.
Each disk type may require operation conditions specific for the disk type. E.g., an optical disk drive may be arranged to scan (read and/or write) a CD-generation disk with a infrared focussing spot using an infrared laser at a numerical aperture of e.g. 0.50 of an objective lens, a DVD-generation disk with a red focussing spot using a red laser at a numerical aperture of e.g. 0.65, and a BD-generation disk with a blue focussing spot using a blue-violet laser at a numerical aperture of e.g. 0.85. Additionally, other operation conditions, such as e.g. scanning velocity, write strategy parameters, servo system settings and read channel settings, may depend on the disk generation, on the disk type in general or on other disk characteristics. Other disk characteristics may e.g. comprise a disk reflectance, a number of information layers on the disk, an optical aberration induced by the optical disk in the optical disk drive (e.g. by disk tilt or other disk-induced aberrations), a start radius of a data area, or any other disk characteristic that may vary from one individual disk to another. For setting the operating conditions for scanning, i.e. reading and/or writing, an optical disk, the optical disk drive may thus be arranged to determine a disk characteristic, e.g. to perform a disk type detection. After the disk characteristic is determined, e.g. after the disk type is detected, the optical disk drive may set the corresponding operating conditions.
In starting-up of an exemplary known optical disk drive, e.g. after loading a new optical disk drive or after powering-on of the optical disk drive, the exemplary known optical disk drive is arranged for determining one or more disk characteristics of the optical disk loaded in the optical disk drive. The one or more disk characteristics typically comprises the disk type. This starting-up can consume considerable time, referred to as startup time, and may take e.g. several seconds in known optical disk drives.
With an exemplary known optical disk drive, determining the disk type comprises checking whether the optical disk comprises a wobble by checking a tracking error signal for the presence of a wobble signal while the optical disk is rotated at a constant, pre-determined disk speed. The absence of a wobble signal may be indicative for the disk type being one of a group of read-only disk types (ROM disk types). When a wobble signal is present, a wobble period may be determined, to discriminate whether the disk type is either a) a DVD-R or DVD-RW, b) a DVD+R, DVD+RW, c) a DVD-Qflix, or d) another unsupported DVD-type disk, as each of these disk types is standardized with its specific wobble period.
Known optical disk drives using known methods to determine a disk characteristic, e.g. to determine the disk type as described in the example above, may require a considerable time before determining the disk characteristic is complete, resulting in a considerable startup time.